1Two things to know about stars and light
Stars are everywhere — and their light takes time to get here
You only need two ideas. Watch each one:
Stars are in every direction
Space is full of stars, near and far. Pick any direction and keep going — there are stars scattered out that way, some close, some unimaginably far.
Light is fast, but not instant
Light travels at a speed. A faraway star's light has to cross all that space to reach you — and that takes time. Light from the most distant stars may still be on its way.
2Two ways the sky could be
A sky that's seen everything vs a sky that hasn't yet
Imagine the same star-packed space two different ways. They make very different skies:
Light from everywhere has arrived
If light from every star, however far, has already reached you, then every direction lands on a star.
Only nearby light has arrived
If only light from closer stars has had time to get here, most directions land on nothing — empty so far.
3Your turn — point and look
Aim a line out into space and see what it hits
Drag your finger across the sky to aim a sightline out into deep space. Some directions stop on a near star. Where there's no near one, your line keeps going, deeper and deeper — hunting for a star far out there.
4The big test
Let light reach farther and farther — what does the sky do? ✨
Same sky, packed with stars at every distance. This dial sets how far light has had time to travel to us. Slide it out and starlight reaches us from deeper and deeper space. Guess first — then run it.
Guess before you slide
Stars fill the sky in every direction. So why isn't the whole night sky glowing white?